The present invention relates to the field of sublimation heat transfer systems, and more particularly to a carousel type system for, and to a related method of, transferring patterns to coatings on articles in an efficient and continuous fashion.
Over the past several years the process of printing by sublimation, that is transforming a solid directly to a vapor, has been used to transfer decorative patterns/images to articles. In this process, sublimable inks/dyes are printed on a transfer sheet and transferred to the articles upon the application of heat and pressure. The transfer sheet is placed in direct contact with a coating on the article that is capable of receiving and retaining the pattern. When heated to a temperature at least as high as the sublimation temperature of the selected inks constituting the pattern, vaporization of the inks/pattern occurs, allowing their absorption into the coating.
Since all substances in vapor form tend to expand, a true-pattern transfer can be achieved only if the sublimated inks/patterns are captured by the heated coating instantly upon vaporization. Accordingly, steady contact between the pattern/transfer sheet and the coating/article under a constant pressure is essential for a superior quality transfer. In addition, both pressure and temperature must be uniformly distributed over the transfer surface in order to avoid blurring and distortion of the transferred pattern. Thus, the elimination of hot or cold spots and/or non-uniform contact between the pattern/transfer sheet and the coating/article is paramount.
Execution of these basic concepts have alluded the industry in the past. While there has been varying degrees of success with several single application sublimation transfer machines since the late 1980""s, much is left to be desired. For example, U.S. Pat No. 4,874,454 to Talalay et al. discloses a sublimation transfer machine that utilizes a flexible heating pad that is pressed against the curved surface of a mug by an enveloping tensioning belt. Although effective in transferring the printed pattern onto the mug, the utilization of the heating pad can result in some blurring or distorting of the transferred pattern. It is believed that this problem results from hot or cold spots and/or induced sliding movement of the transfer sheet caused by the non-uniform contact between the pattern and the mug. In addition, only one article at a time may be printed.
Similarly, the device of U.S. Pat No. 4,943,684 to Kramer suffers the same shortcoming in that it is limited to a single application sublimation transfer, and it has two levered elements and corresponding heating pads which encase an article that are hard to stabilize. During the sublimation process the transfer sheet is prone to shift slightly so as to destroy the sharpness of the image.
Thus, an important aspect of the effort to improve this technology, is to provide a sublimation heat transfer system and related method capable of transferring patterns from transfer sheets to coatings on articles in a more efficient manner, while providing an emphasis on improving the quality of printed image. One aspect of improving the efficiency would be to utilize a plurality of fixtures for receiving the articles and transfer sheets to make the process continuous. Cooperating extendable plungers should be used for engaging and uniformly forcing the articles against the transfer sheets in a repeatable and consistent manner in terms of both pressure and temperature.
Additionally, the transfer system should include the loading/unloading of articles in an easy manner, and by operating in a continuous manner with the minimum of operator involvement. As a result, overall increased operating efficiency is accomplished while significantly reducing, if not eliminating, the occurrence of blurred or distorted printed articles.
Accordingly, it is a primary object of the present invention to provide a novel and improved sublimation heat transfer system and related method that are particularly adapted to provide improved operating efficiency, in order to overcome the limitations of the prior art.
Another object of the present invention is to provide a sublimation heat transfer system that is particularly adapted for transferring patterns to multiple articles in a continuous fashion.
It is yet another object of the present invention to provide a sublimation heat transfer system having a carousel for moving an article and a transfer sheet in an endless path through loading/unloading portions, and through a transfer portion where heat is applied.
Still another object of the present invention is to provide a novel and improved method of transferring a pattern from a transfer sheet to a coating on an article moving around a carousel of a sublimation heat transfer system.
Yet another object of the present invention is to provide a sublimation heat transfer system which utilizes a plurality of fixtures and plungers attached to a carousel for transferring patterns to multiple articles in a continuous fashion.
Additional objects, advantages, and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects of the present invention as described herein, an improved sublimation heat transfer system is provided for transferring patterns from transfer sheets to coatings on one or more articles. More specifically, the sublimation heat transfer system includes a carousel for moving each article and transfer sheet in an endless path through loading/unloading portions, and through a transfer portion within an oven for heating.
A driver for the carousel imparts smooth motion to the carousel and the attached fixtures and plungers, which are arranged in groups around the periphery. The oven surrounding the carousel provides the even heat to activate the coating on the article and the ink on the transfer sheet to cause the controlled sublimation desired. As a result, the process operates in a highly efficient manner, and advantageously generates superior and sharper images on the articles.
An actuator acts to extend the plungers along the loading portion of the endless path for forcing the transfer sheets firmly against the coatings of the articles throughout the transfer portion. In accordance with an important aspect of the present intention, the transfer portion is extended a distance and the speed of the carousel is regulated to maintain the heat for a sufficient time to effect the transfer. The actuator further acts to retract the plungers along the unloading portion of the endless path for removal of the printed articles and the spent transfer sheets.
In the most preferred embodiment, the actuator for the plunger is a cam along the lower part of the oven that contacts and extends the plunger along the loading portion of the carousel""s endless path. More specifically, self-aligning cam followers are attached to the plungers for contacting the cam along the loading/unloading portions. The angled mounting of the followers prevents binding of the support spindle for the plunger. Throughout the transfer portion during passage through the oven, the cam follower rides atop the cam thereby maintaining the force applied to the transfer sheets against the coatings of the articles in a consistent manner. Advantageously, in this manner both pressure and temperature are uniformly applied to the transfer sheet and articles, thus avoiding blurring or distorting of the transferred images. It has been found that hot or cold spots and non-uniform pressure between the transfer sheets and the articles is effectively eliminated.
Additionally, the fixtures are formed of metal to form an efficient heat sink in order to assist in the uniform distribution of thermal energy to the articles/coatings during movement along the transfer portion of the endless path. Preferably, the fixtures include a low-friction insert for receiving the articles and the transfer sheets and for pressing the transfer sheets against the coatings of the articles upon full extension of the plungers. A resilient backing is further included for cushioning the articles and transfer sheets. Advantageously, the natural resiliency of the insert and backing provide compensation for any irregularities, including such things as minor misalignments of the plungers/fixtures or the size of the articles relative the fixtures.
In one of the most preferred embodiments, an ejection pin is provided in association with the fixtures to automatically eject the printed articles from the fixtures along the unloading portion of the endless path. Specifically, a second cam along the upper part of the oven along the path extends an ejection pin associated with each fixture for ejecting the printed articles and the spent transfer sheet. In this manner, the printed articles are smoothly transitioned from the fixtures onto the plungers for removal by the operator just as the plunger is lowered. A spring acts to retract the pin as the upper cam is cleared in readiness for the next cycle. The printed articles are thus gently freed from the fixtures and subsequently lowered by the plungers for removal along the unloading portion of the endless path.
In a further aspect of the present invention, in accordance with its objects and purposes, a method of transferring patterns from transfer sheets to coatings on articles moving around a carousel of a sublimation heat transfer system includes positioning fixtures and cooperating plungers for receiving the articles and the transfer sheets on the carousel, driving the carousel in an endless path including loading/unloading and transfer portions loading the articles/sheets on the plungers one at a time, extending the plungers in sequence on the carousel for engaging the articles and the transfer sheets with the fixtures, and activating the coatings on the articles for receipt of the sublimed pattern through heating while moving the articles along the transfer portion of the path, and retracting the plungers for unloading the articles along the unloading portion.
The present preferred method also includes extending the plungers by contacting a lower cam through a cam follower attached to each plunger. The preferred method further includes the steps of receiving and cushioning the articles and the transfer sheets within the fixtures, and pressing the transfer sheets against the articles with the requisite pressure inserts upon full extension of the plungers throughout the transfer portion.
Following the transfer portion of the endless path, the lower cam releases the cam follower allowing the plunger to rescind from its holding position within the fixtures. At approximately the same time, ejecting the printed article is carried out by the upper cam engaging the corresponding ejection pin. In this manner, the printed articles are smoothly transitioned from the fixtures onto the plungers for removal by the operator. As each plunger is unloaded in sequence, the operator reloads with a new article surrounded by the transfer sheet to repeat the cycle in a continuous fashion.
Still other objects of the present invention will become readily apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments, and its several details are capable of modifications in various, obvious aspects all without departing from the invention. In one modification, the fixture can take the form of a spring metal C-clamp that serves as the fixture. In this instance, the support spindle for the plunger moves upwardly against the free flange of the clamp to provide the pressure of the transfer sheet against the article. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.